KR102324462B1 - Method and apparatus for scalable video coding using intra prediction mode - Google Patents

Abstract

The present invention relates to a scalable video coding method and apparatus using an intra prediction mode. The decoding method includes a maximum probability mode set for predicting an intra prediction mode for a decoding target block of an enhancement layer to include an intra prediction mode for a corresponding block of a reference layer. constructing; and reconstructing the decoding object block of the enhancement layer by using any one of intra prediction modes included in the maximum probability mode set.

Description

Intra prediction mode scalable coding method and apparatus {METHOD AND APPARATUS FOR SCALABLE VIDEO CODING USING INTRA PREDICTION MODE}

The present invention relates to image processing technology, and more particularly, to a scalable video coding method and apparatus for encoding/decoding an image.

Recently, as broadcasting services with HD (High Definition) resolution (1280x720 or 1920x1080) have been expanded not only in Korea but also worldwide, many users are getting used to high-resolution and high-definition images. is being applied In addition, along with HDTV, as interest in Ultra High Definition (UHD) having a resolution four times higher than that of HDTV has increased, video standardization organizations have recognized the need for compression technology for higher resolution and higher quality images. In addition, through higher compression efficiency than H.264/AVC (Advanced Video Coding), which is a video compression coding standard currently used for HDTV and mobile phones, it provides the same image quality as the existing coding method, while providing many benefits in terms of frequency band and storage. A new standard that can be provided is required. Currently, MPEG (Moving Picture Experts Group) and VCEG (Video Coding Experts Group) are jointly working to standardize HEVC (High Efficiency Video Coding), which is a next-generation video codec. The outline goal of HEVC is to encode images including UHD images with twice the compression efficiency of H.264/AVC. HEVC can provide not only HD and UHD images, but also 3D broadcasting and high-definition images at lower frequencies than the present in mobile communication networks.

In HEVC, a prediction image may be generated by spatially or temporally prediction of an image, and a difference between the original image and the predicted image may be encoded. By such predictive encoding, the efficiency of image encoding may be increased.

An object of the present invention is to provide a scalable video coding method and apparatus capable of improving encoding/decoding efficiency.

In a scalable video decoding method according to an embodiment of the present invention for solving the above problems, a maximum probability mode set for predicting an intra prediction mode for a decoding target block of an enhancement layer is provided. configuring to include an intra prediction mode for a corresponding block of a reference layer; and reconstructing the decoding object block of the enhancement layer by using any one of intra prediction modes included in the maximum probability mode set.

The scalable video decoding apparatus according to an embodiment of the present invention is configured such that a maximum probability mode set for predicting an intra prediction mode for a decoding object block of an enhancement layer includes an intra prediction mode for a corresponding block of a reference layer. a mode set configuration unit; and a mode selector that selects one of the intra prediction modes included in the maximum probability mode set as the intra prediction mode for the decoding object block of the enhancement layer.

According to an embodiment of the present invention, the number of bits required for encoding and decoding is reduced by configuring the maximum probability mode set for predicting the intra prediction mode of the enhancement layer to include the intra prediction mode for the corresponding block of the reference layer. Thus, coding efficiency can be increased, and thus, improved image quality can be provided at the same bit rate.

In addition, according to another embodiment of the present invention, the pixel values of the corresponding block of the reference layer are corrected using the correlation parameter obtained according to the neighboring pixel values reconstructed in the enhancement layer and the reference layer for the decoding target block of the enhancement layer. By using it as a prediction signal, coding efficiency can be improved.

1 is a block diagram illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of an image decoding apparatus to which the present invention is applied according to an embodiment.
3 is a conceptual diagram illustrating intra prediction modes used in an embodiment of the present invention.
4 is a conceptual diagram schematically illustrating an embodiment of a multi-layer-based scalable video coding structure.
FIG. 5 is a block diagram illustrating a configuration of an intra prediction unit shown in FIG. 2 according to a first embodiment.
6 is a flowchart illustrating a scalable video coding method according to the first embodiment of the present invention.
7 is a diagram for describing a first embodiment of an inter-layer intra prediction method.
8 is a table showing an embodiment of the number of selectable intra prediction modes according to a block size.
9 is a flowchart illustrating a scalable video coding method according to a second embodiment of the present invention.
10 is a flowchart illustrating a scalable video coding method according to a third embodiment of the present invention.
11 is a block diagram illustrating a configuration of an intra prediction unit shown in FIG. 2 according to a second embodiment.
12 is a flowchart illustrating a scalable video coding method according to a fourth embodiment of the present invention.
13 is a diagram for describing a second embodiment of an inter-layer intra prediction method.
14 is a table illustrating an example of an intra prediction mode additionally selectable in an enhancement layer according to block sizes of an enhancement layer and a reference layer.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

When it is said that a component is "connected" or "connected" to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be In addition, the description of "including" a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

In addition, the components shown in the embodiment of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is composed of separate hardware or a single software component. That is, each component is listed as each component for convenience of description, and at least two components of each component are combined to form one component, or one component can be divided into a plurality of components to perform a function, and each Integrated embodiments and separate embodiments of components are also included in the scope of the present invention without departing from the essence of the present invention.

In addition, some of the components are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention, except for components used for performance improvement, and a structure including only essential components excluding optional components used for performance improvement Also included in the scope of the present invention.

1 is a block diagram illustrating a configuration of an image encoding apparatus to which the present invention is applied according to an embodiment.

Referring to FIG. 1 , the image encoding apparatus 100 includes a motion prediction unit 111 , a motion compensation unit 112 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , and a transform unit 130 . , a quantizer 140 , an entropy encoder 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference image buffer 190 .

The image encoding apparatus 100 encodes an input image in an intra mode or an inter mode and outputs a bitstream. Intra prediction refers to intra prediction, and inter prediction refers to inter prediction. In the intra mode, the switch 115 is switched to intra, and in the inter mode, the switch 115 is switched to inter. The image encoding apparatus 100 generates a prediction block for an input block of an input image, and then encodes a difference between the input block and the prediction block.

In the intra mode, the intra prediction unit 120 generates a prediction block by performing spatial prediction using pixel values of an already coded block around the current block.

In the inter mode, the motion prediction unit 111 obtains a motion vector by finding a region that best matches the input block in the reference image stored in the reference image buffer 190 during the motion prediction process. The motion compensator 112 generates a prediction block by performing motion compensation using a motion vector.

The subtractor 125 generates a residual block by the difference between the input block and the generated prediction block. The transform unit 130 performs transform on the residual block and outputs a transform coefficient. The quantization unit 140 quantizes the input transform coefficient according to the quantization parameter and outputs a quantized coefficient. The entropy encoding unit 150 entropy-encodes the input quantized coefficients according to a probability distribution and outputs a bit stream.

Since HEVC performs inter prediction encoding, that is, inter prediction encoding, the currently encoded image needs to be decoded and stored to be used as a reference image. Accordingly, the quantized coefficients are inverse quantized by the inverse quantization unit 160 and inversely transformed by the inverse transform unit 170 . The inverse-quantized and inverse-transformed coefficients are added to the prediction block through the adder 175, and a reconstructed block is generated.

The reconstructed block passes through the filter unit 180, and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or the reconstructed picture. can do. The filter unit 180 may be referred to as an adaptive in-loop filter. The deblocking filter can remove block distortion at the boundary between blocks. The SAO may add an appropriate offset value to a pixel value to compensate for a coding error. ALF may perform filtering based on a comparison value between the reconstructed image and the original image, and may be performed only when high efficiency is applied. The reconstructed block passing through the filter unit 180 is stored in the reference image buffer 190 .

2 is a block diagram illustrating a configuration of an image decoding apparatus to which the present invention is applied according to an embodiment.

Referring to FIG. 2 , the image decoding apparatus 200 includes an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , a motion compensator 250 , and a filter unit. 260 and a reference image buffer 270 .

The image decoding apparatus 200 receives the bitstream output from the encoder, performs decoding in an intra mode or an inter mode, and outputs a reconstructed image, that is, a reconstructed image. In intra mode, the switch is switched to intra, and in inter mode, the switch is switched to inter. The image decoding apparatus 200 obtains a residual block from the received bitstream, generates a prediction block, and then adds the residual block and the prediction block to generate a reconstructed block, that is, a reconstructed block.

The entropy decoding unit 210 entropy-decodes the input bitstream according to a probability distribution and outputs a quantized coefficient. The quantized coefficient is inverse quantized by the inverse quantization unit 220 and inversely transformed by the inverse transformation unit 230 . As a result of inverse quantization/inverse transformation of the quantized coefficient, a residual block is generated.

In the intra mode, the intra prediction unit 240 generates a prediction block by performing spatial prediction using pixel values of an already coded block around the current block.

In the inter mode, the motion compensator 250 generates a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference image buffer 270 .

The residual block and the prediction block are added through the adder 255 , and the added block passes through the filter unit 260 . The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a reconstructed block or a reconstructed picture. The filter unit 260 outputs a reconstructed image, that is, a reconstructed image. The restored image may be stored in the reference image buffer 270 and used for inter prediction.

* Methods for improving the prediction performance of an encoding/decoding device include a method of increasing the accuracy of an interpolation image and a method of predicting a difference signal. Here, the difference signal is a signal indicating a difference between the original image and the predicted image. In the present invention, "difference signal" may be replaced with "difference signal", "residual block" or "difference block" depending on the context, and those of ordinary skill in the art can affect the spirit and essence of the invention. You will be able to distinguish them within the range not given.

Even if the accuracy of the interpolated image is increased, a difference signal is inevitably generated. Therefore, it is necessary to improve the encoding performance by reducing the difference signal to be encoded as much as possible by improving the difference signal prediction performance.

As a method of predicting a difference signal, a filtering method using a fixed filter coefficient may be used. However, this filtering method has limitations in prediction performance because filter coefficients cannot be adaptively used according to image characteristics. Therefore, it is necessary to improve the accuracy of prediction by performing filtering according to the characteristics of each prediction block.

Meanwhile, the encoding target block is a set of spatially connected pixels in the current encoding target image. An encoding target block is a unit for encoding and decoding, and may be a rectangle or an arbitrary shape. The peripheral reconstruction block is a block that is encoded and decoded before the current encoding target block is encoded in the current encoding target image.

The prediction image is an image in which prediction blocks used for encoding each block from the first encoding object block of the image to the current encoding object block in the current encoding object image are collected. Here, the prediction block refers to a block having a prediction signal used for encoding each encoding object block in a current encoding object image. That is, the prediction block refers to each block in the prediction image.

The neighboring block means a neighboring reconstructed block of the current encoding target block and a neighboring prediction block that is a prediction block of each neighboring reconstructed block. That is, the neighboring block refers to both the neighboring reconstruction block and the neighboring prediction block.

The prediction block of the current encoding target block may be a prediction block generated by the motion compensator 112 or the intra prediction unit 120 according to the embodiment of FIG. 1 . In this case, after the prediction block filtering process for the prediction block generated by the motion compensator 112 or the intra prediction unit 120 is performed, the subtractor 125 performs a difference between the filtered final prediction block and the original block. can

The neighboring blocks may be blocks stored in the reference image buffer 190 or a separate memory in the embodiment of FIG. 1 . In addition, a neighboring reconstruction block or a neighboring prediction block generated in an image encoding process may be used as a neighboring block as it is.

3 is a conceptual diagram illustrating intra prediction modes used in an embodiment of the present invention.

Referring to FIG. 3 , a different number of selectable intra prediction modes may exist according to a block size of a coding unit (CU).

That is, by using a different number of intra prediction modes according to the size of the coding unit (CU), an intra prediction direction may be determined according to the size of an encoding (or decoding) target block, and efficient intra prediction may be performed.

For example, in the case of H.264/AVC, there are 9 selectable intra prediction modes for a 4x4 luma block, and there are 4 selectable intra prediction modes for a 16x16 luma block and a chrominance component.

Meanwhile, in HEVC, there may be 18 selectable intra prediction modes for a 4x4 luma block, 35 for an 8x8/16x16/32x32 luma block, and 4 selectable intra prediction modes for a 64x64 luma block.

The 35 selectable intra prediction modes may each have a direction and a mode value as shown in FIG. 3, and some of the 35 intra prediction modes shown in FIG. 3 are selected for a 4x4 luma block and a 64x64 luma block. It may be possible.

The encoding apparatus 100 selects a prediction mode that minimizes a difference between a prediction block and an encoding object block from among selectable intra prediction modes according to the block size of the encoding unit (CU), and decodes the selected intra prediction mode. An intra prediction mode signal may be signaled to inform 200 .

In addition, since the intra prediction mode of the encoding object block and its neighboring blocks may be related to each other, the intra prediction mode of the encoding object block is divided into intra prediction modes of neighboring blocks (eg, the left block and the upper block). It can be predicted and signaled to a decoding device.

4 is a conceptual diagram schematically illustrating an embodiment of a scalable video coding structure using a plurality of layers to which the present invention can be applied. In FIG. 4 , a group of pictures (GOP) indicates a picture group, that is, a group of pictures.

In order to transmit image data, a transmission medium is required, and its performance is different for each transmission medium according to various network environments. A scalable video coding method may be provided for application to such various transmission media or network environments.

The scalable video coding method is a coding method that improves encoding/decoding performance by removing inter-layer redundancy by utilizing texture information, motion information, residual signals, etc. between layers. The scalable video coding method may provide various scalability in terms of spatial, temporal, and picture quality according to ambient conditions such as a transmission bit rate, a transmission error rate, and a system resource.

Scalable video coding may be performed using a structure of multiple layers so as to provide a bitstream applicable to various network situations. For example, the scalable video coding structure may include a base layer that compresses and processes image data using a general image encoding method, and compresses the image data using both encoding information of the base layer and a general image encoding method. It may include an enhancement layer to process.

Here, the layer refers to a set of images and bitstreams classified based on space (eg, image size), time (eg, encoding order, image output order), image quality, complexity, etc. it means. Also, a plurality of layers may have dependencies on each other.

Referring to FIG. 4 , for example, a base layer may be defined as a Quarter Common Intermediate Format (QCIF), a frame rate of 15 Hz, and a bit rate of 3 Mbps, and the first enhancement layer is a Common Intermediate Format (CIF) Format), a frame rate of 30 Hz, and a bit rate of 0.7 Mbps, and the second enhancement layer may be defined as standard definition (SD), a frame rate of 60 Hz, and a bit rate of 0.19 Mbps. The format, frame rate, bit rate, etc. are an example and may be differently determined as needed. Also, the number of layers to be used is not limited to the present embodiment and may be determined differently according to circumstances.

At this time, if a CIF 0.5Mbps bitstream is required, the bitstream may be cut and transmitted so that the bitrate becomes 0.5Mbp in the first enhancement layer. The scalable video coding method may provide temporal, spatial, and picture quality scalability by the method described above in the embodiment of FIG. 3 .

Hereinafter, a target layer, a target image, a target slice, a target unit, a target block, a target symbol, and a target bin mean a layer, an image, a slice, a unit, a block, a symbol, and a bin that are currently encoded or decoded, respectively. Thus, for example, the target layer may be a layer to which the target symbol belongs. In addition, other layers are layers excluding the target layer, meaning layers available in the target layer. That is, another layer may be used to perform decoding in the target layer. Layers available in the target layer may include, for example, temporal, spatial, and picture quality lower layers.

Hereinafter, a corresponding layer, a corresponding image, a corresponding slice, a corresponding unit, a corresponding block, a corresponding symbol, and a corresponding bin are respectively a target layer, a target image, a target slice, a target unit, a target block, a target symbol, a layer corresponding to the target bin; It means an image, a slice, a unit, a block, a symbol, and a bin. The corresponding image means an image of a different layer existing on the same time axis as the target image. If the display order of the image in the target layer and the image in the other layer is the same, it can be said that the image in the target layer and the image in the other layer exist on the same time axis. Whether the images exist on the same time axis may be identified using an encoding parameter such as a picture order count (POC). The corresponding slice refers to a slice that exists in the corresponding image at a position spatially identical or similar to the target slice of the target image. The corresponding unit refers to a unit that exists in the corresponding image at a location that is spatially identical to or similar to a target unit of the target image. The corresponding block refers to a block that exists in the corresponding image at a position spatially identical to or similar to the target block of the target image.

Hereinafter, a slice indicating a unit into which an image is divided is used as a general term for division units such as a tile and an entropy slice. Independent image encoding and decoding is possible between each divided unit.

Hereinafter, a block means a unit of image encoding and decoding. When encoding and decoding an image, the encoding or decoding unit refers to the divided unit when encoding or decoding an image by dividing one image into subdivided units. Therefore, a macroblock, a coding unit (CU), and a prediction unit (PU) : It may be called a prediction unit, a transform unit (TU), a transform block, and the like. One block may be further divided into smaller sub-blocks.

In consideration of the characteristics of scalable video coding as described above, inter-layer intra prediction, inter-layer inter prediction, or inter-layer differential signal prediction may be performed to remove inter-layer redundancy.

The inter-layer intra prediction is a method of using the reconstructed pixel value of a reference layer as a prediction signal after expanding it to suit the resolution of the enhancement layer, and a detailed description thereof will be described in detail below.

Hereinafter, a scalable video coding method according to an embodiment of the present invention will be described in detail with reference to FIGS. 5 to 10 . Meanwhile, a method of coding the enhancement layer as described with reference to FIG. 4 will be described below.

5 is a schematic block diagram illustrating the configuration of a decoding apparatus according to an embodiment of the present invention, and shows a detailed configuration of the intra prediction unit 240 shown in FIG. 2 .

Referring to FIG. 5 , the intra prediction mode adjuster 241 may adjust the intra prediction mode for a block of a reference layer corresponding to a decoding object block of the enhancement layer.

The mode set configuration unit 242 may configure the maximum probability mode set to predict the intra prediction mode for the decoding object block of the enhancement layer.

The maximum probability mode set includes intra prediction modes that are highly likely to be used for the decoding object block of the enhancement layer, and may include, for example, two intra prediction modes that are most likely.

According to an embodiment of the present invention, when the block of the reference layer corresponding to the decoding object block of the enhancement layer has the intra prediction mode, the intra prediction mode adjuster 241 sets the intra prediction mode to that of the intra prediction mode of the enhancement layer. It can be adjusted according to the number and block size.

For example, when the intra prediction mode of the block of the reference layer corresponding to the decoding object block of the enhancement layer is greater than the number of intra prediction modes of the decoding object block of the enhancement layer, the corresponding value is the prediction for the intra prediction mode of the enhancement layer The value is adjusted to a value smaller than the number of intra prediction modes of the enhancement layer so that it can be used as a value. Otherwise, the intra prediction mode value for the corresponding block of the reference layer is not changed.

According to an embodiment of the present invention, the mode set configuration unit 242 may configure the maximum probability mode set for the decoding target block of the enhancement layer to include the adjusted intra prediction mode for the corresponding block of the reference layer. have.

For example, the reference layer may be a base layer.

Meanwhile, the mode selector 243 may select one of the intra prediction modes belonging to the maximum probability mode set configured as described above as a prediction value for the intra prediction mode for the decoding object block of the enhancement layer. That is, the intra prediction unit 240 performing intra prediction on the enhancement layer can more effectively predict the intra prediction mode for the decoding object block of the enhancement layer by referring to the intra prediction mode for the corresponding block of the reference layer. let there be

The intra prediction unit 240 uses the intra prediction mode bit signaled by the encoding apparatus 100 to use the intra prediction mode belonging to the maximum probability mode set configured as described above, and the final intra to be applied to the decoding object block of the enhancement layer. A prediction mode may be selected and a prediction signal may be generated through intra prediction.

This means that, according to the correlation between the corresponding blocks between the enhancement layer and the reference layer (eg, the base layer), the intra prediction mode for the decoding object block of the enhancement layer is the intra prediction mode for the corresponding block of the reference layer. because it is more likely to coincide with Accordingly, encoding/decoding efficiency may be improved.

6 is a flowchart illustrating a scalable video coding method according to the first embodiment of the present invention. Blocks showing the configuration of a decoding apparatus according to an embodiment of the present invention shown in FIG. Let me explain it with help.

Referring to FIG. 6 , the intra prediction mode adjusting unit 241 that adjusts the mode of the reference layer in order to predict the intra prediction mode of the decoding object block of the enhancement layer among the intra prediction unit 240 is applied to the corresponding block of the reference layer. Adjusts the intra prediction mode for , based on the context information of the enhancement layer (step S300).

The mode set constructing unit 242 derives an adjusted intra prediction mode for a corresponding block of the reference layer (step S310).

Thereafter, the mode set configuration unit 242 configures the maximum probability mode set for predicting the intra prediction mode for the decoding object block of the enhancement layer to include the intra prediction mode for the corresponding block of the reference layer ( step S320).

The mode selector 243 selects one of the intra prediction modes included in the configured maximum probability mode set according to the intra prediction mode signal signaled from the encoding apparatus 100 (step S320 ).

The intra prediction unit 240 generates an intra prediction mode of the enhancement layer using the intra prediction mode selected by the above steps and a flag related to intra prediction mode prediction, and uses the intra prediction mode to decode the enhancement layer. Blocks can be restored.

Referring to FIG. 7 , the mode set constructing unit 242 predicts the intra prediction mode for the decoding object block B1 of the enhancement layer, the adjusted intra prediction mode for the corresponding block B2 of the base layer. The maximum probability mode set can be reconstructed to include.

For example, the corresponding block B2 of the base layer is a block that best matches the decoding target block B1 of the enhancement layer among blocks existing in the base layer, or the decoding target of the enhancement layer It may be a block (co-located block) having a position corresponding to the block B1.

Referring to FIG. 8 , when the size of the decoding object block of the enhancement layer is 64x64, the intra-prediction mode adjuster 241 determines that the intra-mode of the reference layer is greater than 3 (= the number of intra-prediction modes of the 64x64 block -1). If it has, adjust the corresponding intra mode in the range of 0~3.

As another example, when the size of the decoding target block of the enhancement layer is 4x4, when the intra mode of the reference layer has a value greater than 17 (= the number of intra prediction modes of the 4x4 block-1), the corresponding intra mode is set from 0 to 18 adjust to the range of

Hereinafter, an embodiment of a method of configuring the maximum probability mode set in step S310 will be described in detail with reference to FIG. 9 .

Referring to FIG. 9 , the mode set configuration unit 242 first checks whether two referenceable intra prediction modes exist in neighboring blocks of the enhancement layer (step S400 ).

For example, when different intra prediction modes are used for the left block and the upper block of the decoding object block of the enhancement layer, it may be determined that there are two referenceable intra prediction modes.

On the other hand, when either of the left block and the upper block does not use intra prediction (eg, uses inter prediction), or the same intra prediction mode is used for the left block and the upper block, It may be determined that two referenceable intra prediction modes do not exist.

When there are two referenceable intra prediction modes, the mode set constructing unit 242 selects the maximum probability mode set as the minimum value among the intra prediction mode for the corresponding block of the reference layer and the two referenceable intra prediction modes. configure (step S410).

If there are no two referenceable intra prediction modes, the mode set configuration unit 242 checks whether at least one referable intra prediction mode exists in neighboring blocks of the enhancement layer (step S420).

For example, when either one of the left block and the upper block uses intra prediction, or the same intra prediction mode is used for the left block and the upper block, it is determined that there is one referable intra prediction mode can be

On the other hand, when both the left block and the upper block do not use intra prediction, it may be determined that there is no referable intra prediction mode.

When there is one referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include the intra prediction mode of the neighboring block and the intra prediction mode of the corresponding block of the reference layer. (Step S430).

Meanwhile, when there is no referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include an intra prediction mode and a DC mode for a corresponding block of the reference layer (S440). step).

In this case, the encoding apparatus 100 selects one intra prediction mode from among the set of maximum probability modes configured as described above as the intra prediction mode for the decoding object block of the enhancement layer, and then provides information on the selected intra prediction mode. It can be signaled with an intra prediction mode signal.

Hereinafter, an embodiment of a method of configuring the maximum probability mode set when the intra prediction mode of the reference layer is not used will be described in detail with reference to FIG. 10 .

Referring to FIG. 10 , the mode set configuration unit 242 first checks whether two referenceable intra prediction modes exist in neighboring blocks of the enhancement layer (step S500 ).

When there are two referenceable intra prediction modes, the mode set configuration unit 242 configures the maximum probability mode set with the minimum and maximum values of the two referenceable intra prediction modes (step S510).

When there are no two referenceable intra prediction modes, the mode set constructing unit 242 checks whether at least one referable intra prediction mode exists in neighboring blocks of the enhancement layer (step S520).

When there is one referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include the intra prediction mode of the neighboring block and the DC mode or the planar mode (step S530).

Meanwhile, when there is no referenceable intra prediction mode, the mode set configuration unit 242 configures the maximum probability mode set to include the DC mode and the planar mode (step S540).

According to another embodiment of the present invention, the intra prediction unit 240 for reconstructing the decoding object block of the enhancement layer generates a prediction signal for the enhancement layer using pixel values reconstructed with respect to the corresponding block of the reference layer. can do.

For example, before expanding the reconstructed pixel values of the reference layer corresponding to the decoding object block to match the resolution of the enhancement layer, the intra prediction unit 240 may compare with reconstructed pixel values around the corresponding block of the reference layer. Based on a context between the reconstructed neighboring pixel values of the enhancement layer, the reconstructed pixel values of the corresponding reference layer may be filtered and improved. Thereafter, a texture obtained by magnifying a pixel value of the filtered reference layer according to a resolution may be used as a prediction signal for a decoding object block of the enhancement layer.

Hereinafter, a scalable video coding method according to another embodiment of the present invention will be described in detail with reference to FIGS. 11 to 13 .

11 is a block diagram illustrating a second embodiment of the configuration of the intra prediction unit shown in FIG. 2 . The illustrated intra prediction unit 240 includes a context-based parameter calculation unit 245 and a texture generation unit 246 . may include

Referring to FIG. 11 , the context-based parameter calculator 245 based on context information such as reconstructed neighboring pixel values for the decoding target block of the enhancement layer and reconstructed neighboring pixel values for the corresponding block of the reference layer. Correlation parameters (eg, α and β) between the inter-layer reconstructed pixel values can be obtained.

Meanwhile, the texture generator 246 may generate a prediction signal for the decoding target block of the enhancement layer by correcting the reconstructed pixel values of the corresponding block of the reference layer using the obtained correlation parameter.

12 is a flowchart illustrating a scalable video coding method according to another embodiment of the present invention. It will be explained in conjunction with a block diagram.

Referring to FIG. 12 , the decoding apparatus 200 first checks whether a block of a reference layer corresponding to a decoding target block of an enhancement layer is an intra block (step S600 ).

As a result of the check, when the corresponding block of the reference layer is not an intra block, the motion compensator 250 included in the decoding apparatus 200 may perform inter prediction on the decoding object block of the enhancement layer.

Meanwhile, when the corresponding block of the reference layer is an intra block, the decoding apparatus 200 checks whether information of the reference layer is used to perform intra prediction on the decoding object block of the enhancement layer (step S620). ).

When the information of the reference layer is not used, the intra prediction unit 240 included in the decoding apparatus 200 performs intra prediction on the decoding object block of the enhancement layer using only information from the enhancement layer ( step S630).

For example, in step S630, the intra prediction unit 240 generates a prediction block by performing spatial prediction using pixel values of an already encoded block around the current decoding target block of the enhancement layer according to a specific intra prediction mode. can

Meanwhile, when using the reference layer information, the decoding apparatus 200 checks whether texture prediction is possible (step S640 ).

For example, when the reference layer is an inter-slice, pixel values are not reconstructed for the corresponding blocks of the reference layer, and accordingly, a prediction signal for the decoding target block of the enhancement layer is obtained using the reconstructed pixel values of the reference layer. It may not be possible to generate or predict a texture using a correlation parameter representing the context between reconstructed pixel values between layers.

When texture prediction is not possible, the intra prediction unit 240 reconstructs the maximum probability mode set by adding an intra prediction mode to the corresponding block of the reference layer (step S650), and is signaled from the encoding apparatus 100 Intra prediction is performed by selecting one of the reconstructed maximum probability mode sets according to the intra prediction mode signal (step S660).

That is, as the intra prediction method in the case where the texture prediction is not possible, the method described with reference to FIGS. 5 to 10 may be used.

Meanwhile, when texture prediction is possible, the context-based parameter calculator 245 included in the intra predictor 240 obtains a correlation parameter using the reconstructed neighboring pixel values of the enhancement layer and the reference layer (step S670).

Thereafter, the texture generator 246 corrects the reconstructed pixel values of the corresponding block of the reference layer using the obtained correlation parameter (step S680).

Referring to the example shown in FIG. 13 , the context-based parameter calculator 245 is configured to calculate a layer based on context information such as reconstructed neighboring pixel values 711 of a reference layer and reconstructed neighboring pixel values 701 of an enhancement layer. A correlation between inter-reconstructed pixel values may be expressed as parameters (eg, α and β).

The texture generator 246 uses the parameters output from the context-based parameter calculator 245 and the reconstructed pixel values 710 for the corresponding block of the reference layer to match the resolution of the enhancement layer and inter-layer pixels. A texture 700 reflecting the context similarity may be generated, and the generated texture 700 is used as a prediction signal for the decoding object block of the enhancement layer.

For example, the texture generator 246 may generate the texture 700 used as a prediction signal for the decoding object block of the enhancement layer by using Equation 1 below.

In Equation 1, Pred _c [x, y] is the texture 700 predicted by the texture generating unit 246, α, β are parameter values obtained by the context-based parameter calculating unit 245, Rec _L [x,y] is the reconstructed pixel values 710 for the corresponding block of the reference layer, and Rec _L '[x,y] is the reconstructed pixel values 710 for the corresponding block of the reference layer. The values are scaled according to the difference in resolution between the layer and the reference layer.

According to another embodiment of the present invention, the intra prediction unit 240 for reconstructing the decoding object block of the enhancement layer may reuse the intra prediction mode of the corresponding block of the reference layer in the enhancement layer.

For example, when the corresponding block of the reference layer corresponding to the decoding object block is an intra mode and a more granular mode of the block to be decoded of the enhancement layer is used, the intra prediction unit 240 may determine the corresponding block of the reference layer. The intra mode may be additionally used in the intra mode selection process of the enhancement layer.

Hereinafter, a scalable video coding method according to another embodiment of the present invention will be described in detail with reference to FIG. 14 .

FIG. 14 shows the operation of the third embodiment for the configuration of the intra prediction unit shown in FIG. 2 .

14, when the size of the decoding object block of the enhancement layer is 4x4 or 64x64 and the size of the decoding object block of the reference layer is any one of 8x8/16x32/32x32, the predetermined selectable intra prediction modes An intra prediction mode for a corresponding block of the reference layer may be added, so that the number of selectable intra prediction modes for a decoding object block of the enhancement layer may be increased by one.

As described above, adding the intra prediction mode for the corresponding block of the reference layer to the predetermined selectable intra prediction modes means that the number of selectable intra prediction modes for the decoding object block of the enhancement layer is that of the reference layer. This may be performed when the number of selectable intra prediction modes for the corresponding block is smaller than the number.

In the above, the scalable video coding method and apparatus according to an embodiment of the present invention have been described with a focus on the video decoding method and apparatus. It may be implemented by performing a series of steps according to the decoding method as described with reference to FIG. 14 .

Specifically, the scalable video encoding method and apparatus according to an embodiment of the present invention performs intra prediction having the same configuration as that of the decoding method and apparatus described with reference to FIGS. An intra prediction mode may be selected, and a prediction signal may be generated according to the selected intra prediction mode.

In the above embodiment, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in a different order or concurrently with other steps as described above. have. In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The above-described embodiments include examples of various aspects. It is not possible to describe every possible combination for representing the various aspects, but one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

Claims (6)

delete delete delete delete In the video encoding method,
determining whether inter-layer texture prediction is performed on a current picture included in an enhancement layer;
scaling a reconstructed reference picture included in a reference layer used for inter-layer texture prediction, based on a resolution difference between the enhancement layer and the reference layer;
obtaining a prediction pixel value of a current block included in the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block included in the scaled reference picture;
obtaining a residual pixel value of the current block by using the prediction pixel value; and
Encoding information on the residual pixel value of the current block through a bitstream,
the correlation parameter comprises a first parameter and a second parameter;
The correlation parameter is calculated based on the reconstructed reference picture,
The prediction pixel value of the current block is obtained by adding the second parameter to a value obtained by multiplying the reconstructed pixel value of the reference block by the first parameter. A computer-readable recording medium storing a bitstream input to an image decoding apparatus to restore an image, comprising:
determining whether inter-layer texture prediction is performed on a current picture included in an enhancement layer;
scaling a reconstructed reference picture included in a reference layer used for inter-layer texture prediction, based on a resolution difference between the enhancement layer and the reference layer;
obtaining a prediction pixel value of a current block included in the current picture by applying a correlation parameter to a reconstructed pixel value of a reference block included in the scaled reference picture;
obtaining a residual pixel value of the current block by using the prediction pixel value; and
Encoding information on the residual pixel value of the current block through the bitstream,
the correlation parameter comprises a first parameter and a second parameter;
The correlation parameter is calculated based on the reconstructed reference picture,
The predicted pixel value of the current block is obtained by adding the second parameter to a value obtained by multiplying the reconstructed pixel value of the reference block by the first parameter. readable recording medium.

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